Electrolyte analyzers are used to analyze the ion components (e.g., sodium, potassium, chlorine, etc.) contained in a biological sample (e.g., blood, urine, etc.). At present, the most frequently used electrolyte analyzers are those involving the use of ion-selective electrodes to measure particular ions in a sample. Such electrolyte analyzers are designed to measure standard solutions of known concentrations in advance to obtain electromotive forces and calculate slopes using the obtained electromotive forces. Such analyzers further measure an internal standard solution and a sample in an alternate manner to obtain their potential difference, thereby measuring the concentrations of particular ions in the sample based on the potential difference. The electrolyte analyzers disclosed in Patent Documents 1 and 2 are examples of the above analyzers.
When ion-selective electrodes are used, a diluent is used to dilute a sample at a particular ratio, and the diluted sample is subjected to measurement. Thus, deterioration of the diluent or mixing of foreign substances into the diluent may result in abnormal measurement data of standard solutions. Because this often occurs after reagent replenishment, it is recommended that, before measurement of a sample, calibration be conducted without reagent replenishment, using new reagents and standard solutions each time.